Cutter bar tensioning means



May 17, 1960 G. JERRlT 2,

CUTTER BAR TENSIONING MEANS Filed Aprill, 195s 2 Sheets-Sheet 2 FIG. 3.

a k/(m $324M m A ttorneys,

CUTTER BAR TENSIONHWG George Jerrit, Glasgow, Scotland, assignorto'Mavor &

This invention relates to machines for mining coal and other mineralsand of the type known as cutter-chain coal-cutters. In a mining machineof this type, an endless cutter chain is supported and guided by a jibwhich extends outwards like an arm from one side of the body of themachine, the chain being led around a powerdriven sprocket wheel in themachine body and being led around a guide at the free end of the jib.

In a mining machine of the type stated provision is made for increasingthe tension of the cutter chain from time to time as the chain becomesworn with use and for slackening the chain whenever the operator has toremove it or if he has overtightenedit.

The object of the present invention is to provide improved means forextending the jib sothat the cutter chain can be tensioned simply,quickly and effectively and for contracting the jib to slacken thecutter chain.

The invention is a mining machine of the cutter-chain type in which thejib has a cylinder-and-plunger device which has a normally closed inletfor the admission of fluent matter under pressure and which is extendedby such matter, when admitted, to extend the jib and so increase thethrust applied by the jib to the cutterchain and is contractible toslacken the chain by opening the inlet.

It is of practical convenience to use grease as the fluent matter bywhich the device is operated, although lubrieating or other liquid mightbe used instead.

An example of a cutter-chain jib embodying the invention is shown in theaccompanying drawings, in which:

Fig. 1 is a plan of the jib showing it partly broken away and insimplified form, constructional details not directly involved in thepresent invention being omitted.

Fig. 2 is a sectional plan, drawn to a larger scale, of thecylinder-and-plunger device.

Fig. 3 is a cross-section on the line HIIII of Fig. 2.

In Fig. 1 there is shown, in simple outline, a portion of the body ofthe cutter-chain type-mining machine which incorporates the cutter-chainjib. As shown, the body has a turret 11 that is rotatable about itscentral vertical axis and encloses a power-driven sprocket 12 whichdrives the cutter chain. The chain itself consists as usual ofinter-linked blocks 13 formed with sockets 14 in which cutter picks 15are secured. In Fig. 1 only a few of these parts 13 to 15 are shown, thecircuit of the picks being indicated by the dash-dot line 16.

In the example, the structure of the cutter-chain jib comprises as usualtwo components, namely: a wide heavy support bar which extends outwardsfrom, being bolted to, the turret 11 in the body of the machine; a jibframe 21 having side members 22 which are a sliding fit along oppositesides of the bar 20 and which serve as straight side guides for thecutter-chain blocks 13. The bar 20 extends radially from thepower-driven sprocket 12, which is coaxial with the turret. The jibframe is provided with a cutter-chain guide 23 at its free end, thisguide in the example consisting of a normally stationary wheel which canbe turned from time-to-time as it becomes worn with United StatesPatent'O use. Thus, as usual, the cutter chain is led in an endless sionand can be caused or permitted to slideinwards in order to slacken thechain. I

The. parts of the example so far described are or may be of usualconstruction. 7

The jib frame 21 is fitted with a cylinder-and-plunger pressure devicethe axis of which is' the longitudinal axis of the jib and by means ofwhich the operator is enabled to force the frame outwards inorder toextend the jib and so increase the chain tension and is enabled to causethe frame to be returned inwards in order to contract the jib and soslacken the chain.

The cylinder is formed in a block 31 with side wings 32 which fit intocomplemental recesses 33 in the frame side members 22. The block 31 issecured to the frame 21 by a heavy screw 31A. The plunger 34 is a simplefree body of cylindrical form which fits into and mates with thecylinder and projects from it, the projecting end of the plunger beingrounded at 35 so as to be suitable for applying a heavy thrust to thesupport bar 20, against which the plunger abuts. The interior end of thecylinder is enlarged to form a compartment 36 into which a duct 37opens. This duct is formed in one of the cylinderblock wings 32 and hasa lateral extension 38 which registers with a duct 39 through the jibframe 21. This duct 39 leads from a fitting 40 which is screwed into themonth of the duct and which is fitted internally with a non-returnspring-pressed ball valve 41 and with a nipple 42 for a grease gun. Thefitting 40 and nipple 42 are enclosed in a recess 43 provided for themin the jib frame 21. This recess normally is closed by a cap 44 screwedinto it; removal of this cap exposes the nipple 42 to the operator.Thus, it will be apparent that the ducts 39, 38, 37 constitute an inletpassage from the recess 43 to the cylinder 30 and that the fitting 40,with its valve 41, constitutes means serving normally to close saidpassage.

Seeing that the duct 37 is drilled from the exterior of the wing 32 inwhich it is provided, the mouth of the duct is blocked by a plug 45secured by a weld 46.

The extent of outward movement of the plunger 34 from the cylinder 30 islimited by escape ducting consisting of an inlet duct 50 extending fromthe inner end of the plunger and lateral outlet ducts 51 which branchfrom the duct 50 to the cylindrical surface of the plunger.

When the coal-cutter is in use, the cylinder 30, compartrnent 36 andducts. 37, 39, 50 and 51 are packed tight with grease, so that theplunger 34 is pressed hard against the support bar 20. By this means thejib frame 21 is thrust outwards against the reaction of the bar 20, andthe cutter chain 1315 is tensioned. In order either to increase thetension or-slacken the chain the operator removes the cap 44. If thetension has to be increased he applies a grease gun to the nipple 42 andforces into the cylinder block 31 as much more grease as may benecessary, so that the device is extended and the jib is equallyextended. If instead the chain has to be slackened he unscrews thefitting 43 so that grease will be discharged from the cylinder block.

The ducting 50, 51 serves as an escape port defining the limit of theplungers movement during extension of the cylinder-and-plunger device.That is to say, if the plunger is forced outwards (i.e. towards theright as viewed in Figs. 1 and 2) so far that the lateral ducts 51 movebeyond the cylinder 30, the grease is discharged as quickly as it ispumped in by the grease gun, so that movement of the plunger ceases.

parts as regards manufacture and incorporation in a coalcutter, even anexisting coal-cutter, and the simplicity and quickness by which thecylinder-and-plunger device can be operated. These advantages areespecially 'important in the case of a jib of complex structure, notablya jib which is one of two or more superposed jibs.

I claim:

1. A mining machine of the cutter-chain type comprising in combination abody, a turret that is rotatable on the body, a power-driven sprocket inthe body co-axial with the turret, a cutter-chain jib composed of two,components, namely an inner component and an outer component one ofwhich is slidable longitudinally relative to the other and the inner ofwhich extends from the turret so as to be rotatable therewith, the outercomponent having an end guide, an endless cutter chain led around saidsprocket and said end guide, a cylinder secured internally within one ofsaid components, a recess in said one of the components, a plunger whichmates with the cylinder and which extends from the cylinder and thrustsagainst the other component, an inlet passage extending from said recessinto the cylinder, and means enclosed (in said recess and normallyclosing said passage but movable to admit fluent matter under pressurethrough said passage into the cylinder to increase the thrust of theplunger against the associated component to tension the cutter chain.

2. A mining machine according to claim 1 in which the means normallyclosing the inlet passage is fitted with a non-return valve and includesa nipple for a grease gun.

3. A mining machine according to claim 1 and including a cap whichcloses the recess. 7

4. A mining machine of the cutter-chain type comprising in combinationabody, a turret that is rotatable on the body, a power-driven sprocket inthe body co-axial with the turret, a cutter-chain jib composed of twocomponents, namely an inner component and an outer component one ofwhich is slidable longitudinally relative to the other and the inner ofwhich extends from the turret so as to be rotatable therewith, the outercomponent having an end guide, an endless cutter chain led around saidsprocket and said end guide, a cylinder secured internally Within one ofsaid components, a recess in said one oi the components, a plunger whichmates with the cylinder and which extends from the cylinder and thrustsagainst the other component, said plunger being a simple cylindricalbody which is free at both ends and which projects from the cylinder toform a one-way connection with the component against which it thrusts,an inlet passage extending from said recess into the cylinder, and meansenclosed in said recess and normally closing said passage but movable toadmit fluent matter under pressure through said passage into thecylinder to increase the thrust of the plunger against the associatedcomponent to tension the cutter chain.

5. A mining machine according to claim 4 in which the means normallyclosing the inlet passage is fitted with a non-return valve and includesa nipple for a grease gun.

References Cited in the file of this patent UNITED STATES PATENTS1,857,376 Hoy May 10, 1932 1,876,024 Rosenberry Sept. 6, 1932 1,931,560Simmons Oct. 24, 1933 2,635,583 Bill Apr. 21, 1953 2,788,883 SchwenkApr. 16, 1957 2,818,311 Ashley Dec. 31, 1957

